On March 20, a man named Keith Clay died in Texas. His death was largely unremarkable except for one thing: he was the 300th person executed in Texas since the U.S. Supreme Court reauthorized capital punishment in 1976. One need not ignore the savagery of his crimes  prosecutors said Clay stood by while a friend murdered a father and his two kids on Christmas Eve 1993, 11 days before Clay himself butchered a store clerk  to pause at his execution.

Three hundred is an impressive milestone, not only because it exceeds the number of executions in the next five top death-penalty states combined, but also because it was reached so quickly. It took nearly two decades for Texas to consummate its first 100 death sentences after 1976--but only five more years to pass 200 and just three after that to hit 300. (The total has since climbed to 306.)

The approach of the 300th execution happened to coincide with a period of intense scrutiny of capital punishment. In January the departing Republican Governor of Illinois, George Ryan, delivered the biggest blow when he commuted the sentences of all 167 people who were to be executed in his state. "Our capital system is haunted by the demon of error," Ryan declared, "error in determining guilt and error in determining who among the guilty deserves to die." He and others argue that problems like racially motivated prosecutions, coerced confessions and unreliable witnesses have made the system capricious. Such worries may help explain why many states with capital punishment  there are 38 in all  seem to be wavering. The number of executions in the U.S., excluding Texas, fell to 38 last year from a peak of 63 in 1999.

Despite the high-profile second-guessing, most Americans favor capital punishment even though they don't fully trust the system that administers it. Not long before the 300th execution in Texas, a poll by the Scripps Howard Data Center found that three-quarters of Lone Star residents supported the death penalty. But a shocking 69% also said they believe the state has executed innocent people. National polls have generated similar results. In a Gallup poll released in May, 73% of the respondents said they thought at least one innocent had been put to death in the previous five years. Yet only about half of Americans favor a moratorium on executions to ensure that those on death row should be there. In other words, most of us believe the death-penalty system is broken  and we don't care.

Which means that if the system's flaws are to be fixed, they must be fixed from within. And because prosecutors have great control over how a murder case is investigated and whether it deserves the death penalty, they will have to drive any meaningful reform. So where do you find a D.A. willing to both ignore public opinion and challenge his colleagues in the criminal-justice system? Surprisingly, in the heart of Texas.

The career of Travis County district attorney Ronald Earle coincides precisely with that of the modern death penalty. Earle was first elected D.A. in 1976, the year the Supreme Court reinstituted capital punishment. At the time, he enthusiastically backed the decision. "I thought it was too simple to talk about," he says in a clipped Texas cadence. But after prosecuting violent crime for a quarter-century, Earle doesn't believe capital punishment is so simple. To be sure, he still supports death for those few brutal murderers he believes would never stop killing, even in prison. And Earle can still summon the swagger of your typical TV district attorney. He says executing serial killer Kenneth McDuff, who is thought to have murdered at least 11 people, was "like shooting a rabid dog."

But like the rest of us, Earle has now watched broken souls walk free after years of wrongful incarceration; 56 have been released from death row in the past decade, either because they were deemed innocent or because of procedural mistakes, according to the Death Penalty Information Center. Unlike the rest of us, Earle still has to enforce the death penalty. He is often plagued by doubts when he must decide whether to seek death. "I agonize over it," he says. "There was a time when I thought the death penalty ought to have wider application, but my views have evolved." Today deciding whether to seek the death penalty is easily the hardest part of his job.

For a D.A., especially one from Texas, Earle is unusually vocal about his doubts. But many other prosecutors share his mix of philosophical support for the death penalty and nagging uncertainty about which cases are right for it. "When I first became prosecutor and had a death-penalty case, I looked forward to it ... Now I get one and dread it," says Stanley Levco, who has been the prosecuting attorney in Vanderburgh County, Ind., since 1991. Levco strongly backs capital punishment, but he says capital cases take so long and cost so much that he wonders which ones are really worth it. "I tell this to the victim's family: there is an excellent chance this person will not die."